RE: Cheese Webcam Booth Frame Rates

[John Selbie <jselbie hotmail com>]

The Lifecam Cinema camera can't do 30fps at YUV or RGB.  There's just not enough USB bandwidth available.  It doesn't even support it when you programatically enumerate it's formats.

But it can do higher frame rates if it's configured to use it's MJPG format.   Requires the jpg filter to decode at that rate.  Uses more CPU.


Lifecam cinema has following formats and max frame rates:

YUY2 at 30fps for multiple formats from 160x120 up to 640x480.
YUY2 at 7.5fps for 800x448, 960x544, and 1280x720
YUY2 at 10fps for 1280x800
MJPG at 30fps for all formats from 160x120 all the way up to 1280x800.

Not sure how Cheese builds the gstreamer graph, but the developers could consider giving priority to MJPG formats over YUV or RGB when the frame rate is higher in that size.

jrs


----------------------------------------
> Subject: Re: Cheese Webcam Booth Frame Rates
> From: bug-track fisher-privat net
> To: s onanski gmail com
> Date: Fri, 29 Apr 2011 07:16:00 +0200
> CC: cheese-list gnome org
>
> On Do, 2011-04-28 at 13:15 -0400, Scott O'Nanski wrote:
> > I noticed Cheese frames rates drop to 10 frames per second in high
> > resolution mode 1280x800 with my Microsoft Live Cam Cinema.
> >
> > Is this a bug? Is there some way to work around it?
>
> Assume you use usb 2.0, it mean maximal possible speed is 480 Mbit/s. If
> you take in count usb and uvcvideo overhead, and may be the quality of
> the cable you may get about 200-300 Mbit/s.
> Now calculate what bandwidth you need to capture 1280x800 30fps:
> 1280 * 800 * 16(for row stream) * 30(fps) = 491 Mbit/s
> Even with theoretical bandwidth, it is impossible to capture this
> stream.
>
> IMHO it is cheese Bug to suggest this kind resolution for video capture.
> It should have two different settings for video and photo. Photo should
> use max resolution, video should use best frame rate.
> --
> Regards,
> Alexey
>
> _______________________________________________
> cheese-list mailing list
> cheese-list gnome org
> http://mail.gnome.org/mailman/listinfo/cheese-list